When we use the Lorentz transform. We must have S,S' frame.
How can we choose S,S' frame?
The S frame is the frame "at rest". Usually, you are in the S frame yourself. But if you are in a moving spaceship, for example, and you are asked what people on a planet read on your clock as you whizz by, they are in the "rest frame" S and you are in the moving frame S'.
Thank you so much.
S and S' can be any two frames moving with a constant relative velocity between them.
It is not necessary that one of them be "at rest".
In usual usage, S must be an inertial frame, which is defined to be one in which Maxwell's equations or your favourite laws of physics in their *standard form* are true.
If you use any particular Lorentz transformation on S, you will obtain S', and S' will also be an inertial frame.
Basically, it tells you how to find all other inertial frames given a particular inertial frame.
So the rest of the laws of physics that aren't my "favourites" don't have to be true to call a frame inertial?
Yeah! Which ones don't you like?
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